In mammals, injury triggers an organised complex cascade of cellular and biochemical events that result in a healed wound. Wound healing is a complex dynamic process that results in the restoration of anatomic continuity and function; an ideally healed wound is one that has returned to normal anatomic structure, function and appearance.
Chronically contaminated wounds all contain a tissue bacterial flora. These bacteria may be indigenous to the patient or might be exogenous to the wound. Closure, or eventual healing of the wound is often based on a physician's ability to control the level of this bacterial flora. Infection of wounds by bacteria delays the healing process, since bacteria compete for nutrients and oxygen with macrophages and fibroblasts, whose activity are essential for the healing of the wound. Infection results when bacteria achieve dominance over the systemic and local factors of host resistance. Infection is therefore a manifestation of a disturbed host/bacteria equilibrium in favour of the invading bacteria. This elicits a systemic septic response, and also inhibits the multiple processes involved in wound healing. Lastly, infection can result in a prolonged inflammatory phase and thus slow healing, or may cause further necrosis of the wound. The granulation phase of the healing process will begin only after the infection has subsided.
In clinical practice, a diagnosis of infection is based on the presence of local pain, heat, swelling, discharge and redness, although many clinical indicators, such as inflammation and discharge, have a low predictive value of infection in wounds. Definitive diagnosis is achieved by microbiological analysis of wound samples. Tissue biopsy provides the most accurate results, but this is an invasive procedure that is difficult to achieve for the mass of specimens required. Wound swabbing is the most common wound sampling method used in the UK although its clinical value has been questioned. Furthermore, microbiological diagnosis of wound infection can take 48 to 72 hours, which allows time for infection to further develop if first-line/best-guess treatment is not employed immediately.
There therefore remains a need in the art for a method for the early diagnosis and prognosis of wound infection, and for devices and wound dressings for use in carrying out such methods.
Vimentin is an intermediate filamentous protein found in many cells types. Its primary function is to play a role stabilizing cell architecture, and it moves along microtubules in the cell and may therefore play a role in cell migration. A detailed review of vimentin is given by Clark and Allan, 2002; Current Biology, 12, R596-R598. It does not contain a signal sequence, is not present in secretory granules and this group of filamentous cytoskeletal proteins. Recently it has been reported that Vimentin could be secreted by activated macrophages in an in vitro model [Mor-Vaknin et al, 2003; in Nature Cell Biology, 5, 63]. Mor-Vaknin et al., however, did not include any in vivo data and made no indication that Vimentin is present in wound fluid or could be a potential marker of infection. Moreover, as a structural intracellular protein it is surprising that this vimentin can be used as a marker of clinical wound infection.
EP-A-1388734 relates to the screening of test sample solutions to determine the level of one or more characteristic markers associated with a medical condition, including inflammatory disorders. Actin is mentioned as a suitable normalisation marker. Suitable test samples include bodily fluids however, these are must contain cells or cell debris which are solubilised in solvent before screening for cell associated markers.
WO00/06730 describes a diagnostic assay for human cytoskeletal proteins (HCYT) in human body fluids. The specification provides a long disease list although there is no explicit mention of inflammatory disorders or bacterial infection of wounds. There is also no disclosure of the use of wound exudate as a substrate source.
WO00/70349 describes the screening of ductal fluid samples for secreted or non-secreted intracellular components as markers of breast cancer. WO99/24054 describes the use of human annexin, tumulin and apolipoprotein B to screen for HCV infection. These proteins were found to bind to the HCV envelope. WO86/03007 describes the detection of damage to cytoskeletal components as a screen for the presence of a toxic substance.